Checked the issue on reported chrome version 64.0.3282.140 using Mac 10.13.1 with the below mentioned steps.
1. Launched chrome
2. Navigated to https://jsfiddle.net/dvgnsLev/
3. Scrolled up and down to check the colour of the scroll bar.
We are able to see light colour of scroll bar as mentioned in comment#0. We further checked the builds in M60(60.0.3072.0) are latest canary 66.0.3346.0 where scrolling on left side has a different behaviour in both versions. Attaching the screen cast of the same.

@Reporter: Could you please check the screen cast and let us know the good and bad behaviours out of those two builds shown in screen cast. Any further inputs from your end may help us to triage the issue in a better way.

Thanks!

Deleted: 811725.mp4 2.3 MB

	811725.mp4 2.3 MB View Download

Thanks for checking it out Vamshi! When you run it in 66 you're only scrolling in the left area. The problem is in the right area only (right area is body scroll and left area is element scroll).

Thank you for providing more feedback. Adding requester "vamshi.kommuri@chromium.org" to the cc list and removing "Needs-Feedback" label.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

As per the confirmation given by reporter in comment#3 checked the issue, we are able to reproduce the issue on Mac 10.13.1 on reported chrome version 64.0.3282.140 and on the latest canary 66.0.3347.0.

Bisect Info:
==================
Last Good build:  62.0.3181.0
First Bad build:  62.0.3182.0

You are probably looking for a change made after 493347 (known good), but no later than 493348 (first known bad).
CHANGELOG URL:
  https://chromium.googlesource.com/chromium/src/+log/6f8907e8f4671c64be90dcfe162b483ded6f4c29..9f25abddd6a5e0d25d5082ec0f29727a984f9e03

Suspecting the same.
Review URL: https://chromium-review.googlesource.com/608028

@ericwilligers: Please help in assigning it to others, if not related to your change.

Note: Assigning it to ericwilligers as author "rune" isn't available.

Thanks!

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d2c6bc84dcfbb02ceeb0ce39aeb68a8d167e1cf8

commit d2c6bc84dcfbb02ceeb0ce39aeb68a8d167e1cf8
Author: Rune Lillesveen <futhark@chromium.org>
Date: Fri Feb 16 02:53:46 2018

Update scrollbar theme after viewport propagation.

We used to pass through html and body style recalc twice for viewport
style propagation. When we moved to propagating such styles to after the
style recalc, the viewport style is not up-to-date right after body style
is calculated and overlay scrollbar theming did not update correctly.
Instead move the theme update to PropagateStyleToViewport after style is
set on LayoutView.

Bug:  811725 
Change-Id: If51c580b7162f512377eecb48d85ca71bd5e7628
Reviewed-on: https://chromium-review.googlesource.com/921801
Reviewed-by: Steve Kobes <skobes@chromium.org>
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537149}
[modify] https://crrev.com/d2c6bc84dcfbb02ceeb0ce39aeb68a8d167e1cf8/third_party/WebKit/Source/core/dom/Document.cpp
[modify] https://crrev.com/d2c6bc84dcfbb02ceeb0ce39aeb68a8d167e1cf8/third_party/WebKit/Source/core/layout/LayoutBox.cpp
[modify] https://crrev.com/d2c6bc84dcfbb02ceeb0ce39aeb68a8d167e1cf8/third_party/WebKit/Source/core/layout/ScrollbarsTest.cpp

Thanks for fixing this so quickly! :)